const numbers = ['零', '壹', '贰', '叁', '肆', '伍', '陆', '柒', '捌', '玖'];
const leftUnits = ['元', '拾', '佰', '仟', '万', '拾', '佰', '仟', '亿', '拾', '佰', '仟', '万', '拾', '佰', '仟', '万'];
const rightUnits = ['角', '分'];

const rmb = (value) => {
  if (Object.prototype.toString.call(value) === '[object Number]' && value >= 0.01) {
    const fragment = [];
    const [leftValues, rightValues] = String(value)
      .split('.')
      .map(part => part.split('').map(i => i * 1));

    const leftValueLength = leftValues.length; // 整数部分位数
    const unit1 = leftValueLength - 1; // 元位
    const unit5 = leftValueLength - 5; // 万位
    const unit9 = leftValueLength - 9; // 亿位
    const unit13 = leftValueLength - 13; // 万亿位
    const unit17 = leftValueLength - 17; // 万万亿位
    const hasLeftValue = leftValueLength > 1 || leftValues[0] > 0; // 整数部分不为0
    const hasRightValue = rightValues && (rightValues[0] > 0 || rightValues[1] > 0); // 小数部分不为0
    const has678Value = leftValues[unit5 - 1] > 0 || leftValues[unit5 - 2] > 0 || leftValues[unit5 - 3] > 0; // 拾万、佰万或仟万位不为0
    const overflowIndex = leftValueLength - leftUnits.length; // 溢出位索引

    let leftUnitIndex = 0;
    for (let i = leftValueLength - 1; i >= 0; i--) {
      if (
        leftValues[i] === 0
        && (i === unit5 || i === unit9 || i === unit13 || i === unit17)
        && leftValues[i + 1] > 0
      ) { // 当前位为0，且当前位为万、亿、万亿、万万亿，且低一位不为0
        fragment.unshift(numbers[leftValues[i]]);
      }

      if (
        (leftValues[i] > 0)
        || (i === unit1 && hasLeftValue)
        || (i === unit5 && has678Value)
        || i === unit9
        || i === unit13
        || i === unit17
      ) { // 元、万、亿、万亿、万万亿或当前位不为0
        fragment.unshift(leftUnits[leftUnitIndex]);
      }

      if (
        leftValues[i] > 0
        || (leftValues[i + 1] > 0 && i !== unit5 && i !== unit9 && i !== unit13 && i !== unit17)
        || i <= overflowIndex
      ) { // 当前位不为0，或低一位不为0且当前位非万、亿、万亿、万万亿，或当前为溢出位
        fragment.unshift(numbers[leftValues[i]]);
      }

      leftUnitIndex++;
    }

    if (hasRightValue) {
      // 角
      if (rightValues[0] > 0 || hasLeftValue) { // 角位不为0，或整数位不为0
        fragment.push(numbers[rightValues[0]]);
      }
      if (rightValues[0] > 0) { // 角位不为0
        fragment.push(rightUnits[0]);
      }
      // 分
      if (rightValues[1] > 0) {
        fragment.push(numbers[rightValues[1]]);
        fragment.push(rightUnits[1]);
      }
    } else { // 没有小数位
      fragment.push('整');
    }
    return fragment.join('');
  }
  return '零元整';
};

module.exports = rmb;
